For much of aviation’s supply-chain crisis, attention has remained fixed on the factory. Airbus and Boeing cannot deliver aircraft quickly enough: the global order backlog has crossed 18,000 aircraft, airlines are operating without more than 5,000 newer aircraft they had expected to receive, and the average age of the commercial fleet has reached a record 15.2 years. The industry’s capacity shortage now has a second layer: some aircraft have already been delivered, financed, and added to airline fleets, but remain unavailable due to shortages of serviceable engines, parts, or maintenance slots. Capacity is constrained first at the factory and again in service, where aircraft can sit parked for months awaiting engines. As a result, fleet size becomes less meaningful than the serviceable fleet.
The Aircraft Exists But The Engine is Unavailable
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The Pratt & Whitney Geared Turbofan (GTF) provides the clearest example. At the March 2025 peak, 648 GTF-powered aircraft were in extended storage while operators waited for engine shop visits, spare engines, or parts equivalent to 28% of the GTF-powered fleet. These aircraft were already part of airline fleets but could not operate.
The original disruption involved manufacturing-quality problems, component durability, and reduced time on wing (the number of flight hours or cycles an engine can remain installed before removal for inspection or maintenance). Engines required inspections and removals earlier than planned, creating a secondary bottleneck: repair networks needed to process an abnormal volume of engines while facing shortages of replacement components, spare engines, qualified technicians, specialised tooling, and test-cell capacity.
This volume of work exceeded what the maintenance network was built to process. Engine shops needed to dismantle and inspect more engines while competing for replacement components, spare engines, specialised tooling, test-cell capacity, and qualified personnel. Shop-visit turnaround times had been expected to remain closer to normal maintenance cycles, but some repair periods extended to around 300 days. While an engine remained in the shop, the aircraft frequently remained parked unless the airline could secure a spare engine.
Greater aftermarket competition can help by expanding the number of organisations approved to perform inspections, repairs, and overhauls, giving airlines more options when sourcing certified parts and services. It cannot, however, remove a defect originating in the component itself. An affected turbine or compressor disk must still be inspected and replaced with a conforming part. An additional certified provider cannot make a nonconforming component serviceable or install an approved replacement that has not yet been produced.
The bottleneck extends across several stages: access to maintenance manuals and repair procedures, production of approved components, availability of spare engines, and the physical capacity of shops to process removals. Opening the aftermarket widens the industry’s response, but underlying demand for inspections and replacement parts remains.
Airlines Need Reliable Return Dates
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Scheduled maintenance is a known, budgetable cost built into operational calendars. Unscheduled maintenance is harder and increasingly frequent as the global fleet ages and newer, electronically complex aircraft introduce novel failure modes.
When the FAA grounded all 171 Boeing 737 MAX 9 aircraft after the Alaska Airlines door plug blew out in January 2024, aircraft did not return to service on any planned timeline. The event forced immediate, expensive decisions like cancelled flights, substitute aircraft, and emergency leasing with almost no lead time.
Air New Zealand illustrated this uncertainty in April 2025, expecting 11 aircraft grounded due to additional maintenance requirements affecting Pratt & Whitney engines on its Airbus neo fleet and Rolls-Royce engines on its Boeing 787s. Groundings persisted even after securing seven additional leased engines and another owned spare because manufacturer maintenance timeframes remained unpredictable.
Financial consequences were visible at Wizz Air, where operating profit fell 61.7% in FY2025 as engine groundings constrained capacity. With engine shop visits taking around 300 days, the airline faced a problem beyond higher maintenance costs: it could not confidently determine when a substantial part of its fleet would become available again.
Visibility means more than receiving general delay warnings. Airlines need credible information on expected shop-entry dates, required parts, work completed, and likely engine-release dates. A forecast moving repeatedly from month to month cannot support a stable flying schedule. Better information will not produce a missing component, but it tells an airline whether it needs replacement capacity for a week, a quarter, or an entire season.
Maintenance Data Must Lead to Operational Decisions
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In November 2025, Airbus issued an Emergency Airworthiness Directive requiring around 6,000 A320 family aircraft to receive urgent software updates within days. Following a dangerous in-flight altitude drop on a JetBlue A320 in late 2025, an investigation revealed the software lacked protection against electromagnetic interference that did not appear during scheduled maintenance.
Airlines with better-connected data identify affected aircraft faster and sequence repairs more efficiently. American Airlines identified 209 affected aircraft and updated most on the first day; Air India updated over 40% of its affected fleet without cancellations. While fleet size, location, technician availability, and modification types shaped responses, these differences show how the same directive produces varying operational outcomes depending on how quickly an airline assesses its fleet and coordinates work.
Platforms already support parts sourcing and technical coordination. IATA’s MRO SmartHub provides market information covering over 1.5 million part numbers. The International Airlines Technical Pool connects over 140 airlines across approximately 890 stations for AOG (aircraft-on-ground) contacts, spare parts, and local support.
Platform availability, however, does not equal integration. A 2025 aviation maintenance benchmark found 59% of operators used mixed systems rather than a standardised platform. A McKinsey survey of maintenance organisations found only 6% integrated digital tools at scale across engineering, supply chain, and quality assurance, with over 80% identifying fragmented data and physical record-keeping as major barriers.
This fragmentation matters most when an aircraft becomes unexpectedly unavailable. Engineering records, inventory systems, procurement platforms, and workforce systems must all be queried separately if unconnected. McKinsey estimates digital and AI tools could increase technician productivity by 15% to 35%, while leading organisations report maintenance-cost reductions up to 20%. The immediate operational gain is faster triage: determining within hours which aircraft are affected, what is required, and whether parts, technicians, and facilities can be brought together.
Qualified Labour Determines Release
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Maintenance capacity is constrained by people authorised to perform and certify work. Urgent regulatory inspections raise work volume immediately without increasing licensed engineers, inspectors, or certifying staff. The workforce must complete more work under tight deadlines while supporting the operating fleet.
Boeing estimates the industry will require 710,000 new maintenance technicians over the next 20 years. The immediate allocation problem is maintaining older aircraft kept in service due to delivery delays while training personnel for newer engines. Both compete for hangar space, instructors, and staff. Technicians cannot simply be transferred from legacy engines (CFM56 and V2500 powering thousands of older A320s and 737s) to GTF and LEAP work while airlines depend on legacy fleets to fill capacity gaps.
IATA forecasts annual LEAP shop visits rising from 600–800 in 2025 to over 5,000 by 2040, and GTF visits increasing from around 1,000 to over 2,000. Meeting demand requires type-specific training, approved tooling, and qualified supervisors. The pipeline takes years, but unscheduled events do not wait.
The Fleet Already Exists
Two airlines owning 100 aircraft each may operate at vastly different effective capacities. The gap is increasingly explained by unscheduled events that remove aircraft with little warning and return them unpredictably.
This capacity problem does not appear in order books. An airline waiting years for deliveries is managing a fleet where daily operating capacity depends on engines awaiting shop visits, part availability, and technician access. For these airlines, the next required aircraft may not come from a factory, it may already be parked outside a maintenance hangar.